We propose to continue our work in the biosynthesis, structure, immunology, pathology and electron immunohistochemistry of basement membranes. The main objectives are: 1. The characterization of the biosynthetic subunits of basement membrane using a system characterized by rapid basement membrane synthesis, the parietal yolk sac carcinoma. The biosynthetic units will be metabolically labeled with S35-cystein H3-proline H3-glycine precipitated with specific antibodies, electrophoresed in polyacrylamide gels and their presence demonstrated by fluorography. 2. Antibodies against glomerular basement membrane will be used in electron immunohistochemistry of fetal and hypertrophic glomeruli to define the cell(s) responsible for glomerular basement membrane synthesis. 3. The chain of events leading to the deposition of antigen-antibody complexes in renal glomeruli will be studied by electron immunohistochemistry.